1. Field of the Invention:
This invention relates to laundry detergents, and in particular, to a liquid laundry detergent.
2. Description of the Prior Art:
Prior to the present invention, the most effective laundry detergents have usually been powdered products. Liquid laundry detergents have been known, but in most instances, they have had the drawback that they are not, on an equal-weight basis, as effective as the known powder products.
There are several problems which must or should be taken into account in the preparation of a satisfactory liquid laundry detergent.
One problem is stability. A composition which undergoes substantial changes between when it is formulated and when it can be expected to be used, considering the environments to which it is likely to be exposed, is not one that is useful. There are various kinds of instability. Sometimes a few hours or days of exposure to light or to atmospheric oxygen causes a change; sometimes it takes a few weeks. Some compositions do not withstand the cold or the heat that they would sometimes encounter in being shipped.
Another problem is compatibility. There are compositions which may even perform adequately but, when they are initially composed, are turbid or even non-homogeneous. Naturally, a composition which is turbid or non-homogeneous is commercially very undesirable in comparison to one lacking such a disadvantage.
However stable and compatible a composition may be, it is useless if it does not perform adequately as a laundry detergent. It must wash both natural and synthetic fibers and blends of such fibers. It must give good soil removal and good whiteness retention. The detergent must not damage or roughen the fabrics, or unduly shorten their service lives. It must not be so toxic as to endanger its user, or have a displeasing odor or color, or leave any color or odor on the clothes, or foam too much, or cost too much. It must not remove, along with soil, any permanent-press resin treatment on the fabric. It must not, as an all-purpose laundry detergent, itself have a bleaching effect. It must, to obtain adequate performance in comparison with present commercial products, contain some adequate soil-anti-redeposition agent, and usually one or more fabric-brightener agents as well. It should not contain components which are non-biodegradable or would otherwise render it ecologically undesirable. It must not require conditions of manufacture which are intolerably hazardous.
Even if a composition meets all the above requirements, it can be unsatisfactory--for example, if the composition achieves stability or compatibility only by the inclusion of a fairly large percentage of organic solvent, there can be obtained a composition which is satisfactory in most respects, except for its ability to be shipped easily. Any material with too low a flash point is subject, in shipping, to stringent regulations that add to its cost in the hands of the consumer.
It has been usual, in compounding liquid laundry-detergent compositions, to promote the action of the surfactants by including in the composition an inorganic builder. Most of the known liquid laundry-detergent compositions, thus, comprise a mixture of organic and inorganic components, and the mixture has limited solubility in water.
The concept of promoting the action of nonionic surfactants by including with them an alkanolamine such as monoethanolamine or triethanolamine is not completely new. U.S. Pat. No. 3,869,399, issued Mar. 4, 1975, discloses a concentrated liquid detergent which comprises a mixture of a nonionic surfactant, an anionic surfactant, and ethanolamine. U.S. Pat. No. 3,876,563, issued Apr. 8, 1975, describes a liquid detergent which contains a nonionic surfactant, a zwitterionic surfactant, ethanolamine, and a solvent. These patents teach that the ethanolamine component in such a detergent serves several purposes, such as reducing the viscosity, improving the stability, and acting as a buffering agent. The above-mentioned patents do not, however, lead those skilled in the art to believe that, as we have discovered, excellent liquid laundry-detergent compositions can be made which do not contain anionic or zwitterionic surfactants. These patents do not give those skilled in the art any basis for knowing that liquid laundry-detergents can be made which contain the nonionic surfactant(s), an ethanolamine component, and sodium carboxymethylcellulose. It has not been known that it would be possible to obtain a composition in which fabric brightener(s) and sodium carboxymethylcellulose are compatible with nonionic surfactants and an alkanolamine used to promote the action of such surfactants.